We have identified a six kilobase segment of E. coli DNA which carries the entire metBJLF gene cluster. In collaboration with Dr. G.N. Cohen of the Institut Pasteur we will study the structure of this region of the bacterial chromosome. We have the six kilobase fragment in a lambda transducing phage and have cloned an eight kilobase fragment containing it on an amplifiable plasmid. We plan to map the region with restriction endonucleases and to subclone smaller fragments to localize the individual genes. When we have completed this work we plan to sequence selected portions of the DNA, paying special attention to the control regions preceeding the coding sequences for the structural genes.